Die-cast sides with heavy sheet metal base fastened together with rivets. "Lionel" is rubber stamped on both sides. "Built By Lionel" is molded in the left most panel on each side. Length: 10", Width: 4-9/16", Height: 1-3/4" These bridges are in very good condition with some normal wear on the deck where the track was laid on it. There is also some green layout paint on one edge of one of the bridges and on the bottom of the other.